I don't have my Master Reference guide in front of me, but if that's one of the templates for box joints, then yes, you can use thicker material. I've used 3/4-inch thick stock with a 1/4-inch straight bit to make box joints on my Incra LS-17 fence. Note that you cannot make a full-depth cut in one pass--you should not cut any deeper than your bit is wide, so in my case, I made three passes with the 1/4-inch bit to cut 3/4-inch deep (1/4-inch deep the first pass, then increased depth to 1/2-inch for the second pass, and 3/4-inch deep for the third pass.) Fortunately, the repeatability of the Incra system makes this easy. I could have used a different template and a larger bit, but I prefer the look of the thinner fingers.